With the increasing miniaturization of electronic circuit components and the wide variety of applications for integrated circuit devices, there have been a number of efforts to securely package and mount integrated circuit chips to printed circuit boards. These have included leadless integrated circuit packages which may be inserted into a spring-loaded connector arrangement for purportedly securely retaining and providing electrical contact between the contact lead areas on the integrated circuit package and electrical conductor highways of the printed circuit board. Examples of mounting and connection configurations for this purpose are described in the U.S. Pat. Nos. 4,155,615, to Zimmerman, Jr. et al, 3,910,664, to Pauza et al, 3,877,064 to Scheingold et al, and 4,089,575, to Grabbe.
Basically, each of the schemes described in these patents employs a set of multiple contact connector members, each being spring-loaded or spring-biased to engage contacts provided on the periphery of the integrated circuit package that is to be retained by the connector which is mounted on the printed circuit board. According to the descriptions in the patents, the spring-loaded or biased connector members offer the facility of easy insertion and removal of the integrated circuit chip. Grabbe also mentions the desire to accommodate differences in the coefficients of thermal expansion of the connector and the substrate through a set of cooperating and interlocking spring-biased connector terminals, one of which is mounted to the circuit board and the other of which is mounted on the integrated circuit package. The connector which is mounted on the circuit board has a shape which follows a tortuous path which engages the inner walls of a surrounding plastic frame. When the chip carrier is inserted into the socket comprised of the plastic frame and the tortuous path-shaped terminal, bent around terminal portions of the chip carrier frame engage the terminals at prescribed locations in an effort to provide electrical contact therebetween.
Unfortunately, in each of the types of connectors described in the above patent literature, because the electrical connections between the printed circuit board the integrated circuit chip are to be achieved through mechanical friction-contact, spring-loaded or biased contact connectors, they suffer from drawbacks that limit their application and effectiveness. For example, the spring-loaded connector terminal of each arrangement is comprised of a substantial amount of material, extending from the printed circuit board and following a tortuous path, usually back over itself, to effect the necessary spring action. This usually means that a support member, such as the plastic shield of Grabbe or the housing of Pauza et al, must be provided to support the spring-configured terminal connectors. Not only does this add additional weight to the connector, but it substantially reduces the packaging density for the printed circuit board.
Another drawback is the fact that the connections that are achieved between the integrated circuit package and the printed circuit board are effectively mechanical frictional contacts. An effectively continuous electrical path between the lead contact areas on the integrated circuit chip and the conductor highways on the printed circuit board is not necessarily guaranteed; the chip-to-printed circuit board interconnection highway path is subject to discontinuities in the presence of environmental vibrations.
Because of these drawbacks, the connectors of the type described in the above patent literature are not readily suited for applications which are subject to substantial changes in environmental conditions, such as temperature and vibration. While Grabbe purports to solve the temperature fluctuation problem, he does so by employing a package that significantly reduces the integration density on the printed circuit board, adds considerable weight to the components that are mounted on the board and does not guarantee a permanent electrical connection between the chip and the board.